1. Field of the Invention
The present invention relates to a multicapillary sample preparation device especially useful for handling biological samples. In particular, the multicapillary device is suitable for use with a pipette, micropipette, syringe, or other similar analytical instrument.
2. Background Art
Many biological samples are commonly separated by gel electrophoresis and analyzed by matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS). One disadvantage of these techniques, however, is that analysis is strongly affected by the presence of salts, buffers and low molecular weight organic compounds commonly used in the preparation of biological samples. In order to improve the sensitivity and selectivity of analyses, adsorptive and membranous devices are frequently used to purify and concentrate the sample prior to analysis. Such devices feature a bed of porous adsorbent or a semipermeable membrane fixed in a housing of a suitable dimension and shape that traps desired constituents, while allowing contaminants to pass.
To handle samples in the 0.01 to 100 microgram (μg) range, pipettes, micropipettes, syringes or similar analytical instruments (collectively referred to hereinafter as “pipettes”) are commonly employed. The tip of these pipettes is fitted with one or more adsorptive or membranous plugs capable of purifying, concentrating, or fractionating peptides and other biomolecules.
A principal shortcoming of adsorptive and membranous plugs, however, is that porous materials are generally not effective at separating smaller biomolecules such as proteins and polynucleotides. Porous plugs are also deficient with respect to isolating and purifying larger biological materials and nucleic acids such as DNA, RNA and cells. This shortcoming derives from the fact that during sample processing, molecules must wend through a labyrinth of sponge-like, expansive and porous adsorbent silica.
There is little uniformity, consistency, and reproducibility of porous materials used for sample preparation. Sample loss in existing pipette tips is typically about 40-60%. Poor sample recovery is largely due to the fact that a sample must travel through irregular voids in the porous material, whereby a portion of the sample lodges in small voids and is unrecoverable. Moreover, in order to achieve adequate results, samples must be passed through porous materials multiple times (e.g., ten). The sample preparation devices are usually not reusable and fit poorly with automatic instrumentation because poor sample recovery may give rise to contamination due to sample carry-over.
Spin columns and other apparatus operated by a centrifuge rotor are commonly used for the isolation and purification of biological and nucleic acid samples. However, it is desirable in certain applications to avoid the use of a centrifuge for rotating a specimen to be isolated and purified. This is due, in part, to the fact that horizontal separation may result in centrifugal forces of up to, for example, 4,000 RPM, being exerted on or transmitted along the vertical axis of the spin column and sample in order to achieve satisfactory separation. Air resistance negatively affects the spin column by generating drag and friction, which heat the spin column and its contents. Considerable breakage of sample fragments is unavoidable due to the heat transfer, acute centrifugal force and accompanying air resistance. The impaired quality of biological and nucleic acid samples extracted during spin column and centrifugal processing is highly undesirable to the user.
It can be seen, therefore, that the purification and concentration of biological and nucleic acid samples using porous materials prior to instrumental analysis is time consuming, is poorly reproducible, has low throughput, and requires repeated passing of a sample through the porous plug.
Accordingly, it is an object of the present invention to provide an efficient sample preparation device for use in isolating (immunoassay), purifying and concentrating samples of proteins, peptides, nucleic acids (e.g., DNA and RNA), and other biological materials (e.g., cells) prior to analysis.
It is also an object of the invention to provide a sample preparation device with high sample capacity that increases throughput and reduces sample loss.
It is a further object of the invention to provide a highly reproducible sample preparation device that achieves uniformity, consistency, and nearly identical pathways for sample passage.
It is a still further object of the invention to provide a sample preparation device that is simple, cost-effective, and does not require the use of a silica type porous substrate or special equipment such as a centrifuge.